Acute Respiratory Failure: Approach to the patient with dyspnea Nancy Warner, MD Loma Linda University Emergency Medicine
May 11, 2015
Acute Respiratory Failure:Approach to the patient with dyspnea
Nancy Warner, MDLoma Linda University Emergency Medicine
Definition of Dyspnea
Subjective experience of breathing discomfort
Derives from interactions among multiple physiological, psychological, social and environmental factors
Epidemiology
Shortness of breath is the chief complaint for approx 3.5% of ER visits
Dyspnea-related complaints result in 7.6% of ER visits (cough, chest discomfort)
Most Common Diagnoses presenting with dyspnea
Asthma Chronic Obstructive Pulmonary
Disease Interstitial lung disease Myocardial dysfunction
Pathophysiology
Dyspnea results when ventilatory demand exceeds respiratory function
Alterations in gas exchange, pulmonary circulation, cardiovascular function, respiratory mechanics, or oxygen carrying capacity
Categories of dyspnea
Airway causes Respiratory system dyspnea Cardiovascular system dyspnea
Airway causes
Foreign objects Angioedema Anaphylaxis Infections Airway trauma
Respiratory dysfunction
Controller Ventilatory Pump Gas Exchanger
Controller
Determines the rate and depth of breathing via signals sent to the ventilatory muscles
Related to hypoxia or hypercapnia due to ventilation/ perfusion mismatch
Stimulated by “air hunger” or “urge or need to breath”
Ventilatory Pump Ventilatory muscles and peripheral nerves
which transmit signals to the controller Derangements in the ventilatory pump result
in a sense of increased “work of breathing” Neuromuscular weakness can result in max
effort to achieve required air movement Reduced compliance of the chest wall results
in increase effort for air movement
Gas Exchanger
Consists of alveoli and pulmonary capillaries
Diffusion of oxygen and carbon dioxide
Dyspnea results from destruction of the membrane of the imposition of fluid or inflammatory material
Life- threatening respiratory causes
Pulmonary embolism COPD Asthma Pneumothorax or pneumomediatinum Pulmonary infection Pulmonary edema Pulmonary injury
Cardiovascular Dysfunction
Heart Failure Anemia Deconditioning
Heart Failure
Structural or functional cardiac disorder which impairs the ability of the ventricle to eject blood – reduction in cardiac output
Also occurs from increased pulmonary or systemic venous pressure
Leads to dyspnea by producing hypoxemia or by stimulating pulmonary vascular receptors
Anemia
Can impair oxygen delivery because most oxygen in the blood is hemoglobin bound
Mechanism by which this produces dyspnea is not completely clear but related to cells inability to continue aerobic metabolism
Deconditioning
Ability of the heart to increase maximal cardiac output
Ability of the peripheral muscles to utilize oxygen efficiently for aerobic metabolism
Sedentary existence reduces fitness and can lead to dyspnea with even minimal tasks
Life-threatening cardiac causes Acute coronary syndrome Acute decompensated heart failure Flash pulmonary edema High output heart failure Cardiomyopathy Cardiac arrhythmia Valvular dysfunction Cardiac tamponade
Other causes
Neurologic Stroke Neuromuscular disease
Toxic and metabolic Poisoning (salicylate, carbon monoxide) DKA Sepsis Acute chest syndrome (sickle cell)
More causes
Lung cancer Pleural effusion Intraabdominal process Ascites Pregnancy Massive obesity Hyperventilation and anxiety
Evaluation of Dyspnea
History and Physical Lab and Radiographic testing
History and Physical
General historical features Events leading up to episode Triggers Recent trauma or surgery
Past history New or recurring
Prior intubation Time course
More History Time course Severity Chest pain Trauma Fever Hemoptysis Cough and sputum Medications Tobacco and drugs Psychiatric conditions
Physical Exam
Clinic Danger signs: Depressed mental status Inability to maintain respiratory effort cyanosis
Physical Exam (cont)
Signs suggestive of severe respiratory distress Retractions or accessory muscle use Brief, fragmented speech Inablity to lie supine Profound diaphoresis, dusky skin Agitation or other altered mental
status
Labs and X-rays Oximetry Hemoglobin/ Hematocrit Chest x-ray – lung and heart appearance,
shows fluid and inflammation EKG Cardiac enzymes D-dimer BNP ABG
Approach to Treatment
General appearance of the patient is key to determining immediate need
Always start with ABC (airway/ breathing/ circulation)
Initial Intervention
Provide O2 supplement Place pulse oximetry to determine
hypoxemia and monitor therapy Determine need for breathing
assistance
Breathing Assistance
Positive airway pressure (BiPAP or CPAP)
Assist ventilation with bag-valve-mask or intubation
Treat Specific Cause
Med nebs and steroids (asthma/ COPD)
Antibiotics (pneumonia) Diuretics (CHF)
Disposition
Patients requiring supplemental O2 or those in respiratory distress require admission
Depends on underlying etiology and response to therapy
May be affected by clinical situation or comorbidities
Keep in Mind Normal appearance to breathing dose not
rule out serious underlying etiology Always consider ACS or PE (even if chest pain
is not present) Dyspnea in pregnancy is common but always
consider PE if out of proportion Psychogenic dyspnea is a diagnosis of
exclusion Ambulation is a functional “test” which
provides info on a patients respiratory status